* src/ltlast/formula.hh (has_lbt_atomic_props): New method.
* src/ltlast/formula.cc (printprops): Display it.
* src/ltlast/atomic_prop.cc: Update it.
* src/bin/ltlcheck.cc, src/bin/genltl.cc: Use it.
* doc/tl/tl.tex: Menton has_lbt_atomic_props().